Developer for diazo prints



Patented Jan-12, 9 3 2,308,058

nnvnnornn FOR nmzo rams Clyde A. Crowley and John Bernard Mullen, Chicago, IlL, assignors to The Huey C0,, Chicago, Ill., a corporation Illinois 'No Drawing. Application October 3, 1940,

Serial No. 359,546

11 Claims; (01. 95-6) This invention relates to the development of this process are subject to the discoloration dephoto-prints oi the diazo type, and particularly scribed above. to developers which eliminate or reduce the dis- In other forms of vdiazo printing papers, the coloration which commonly occurs when exposed diazo compound and the azo-dyestufl-formlng and developed diazo prints are exposed to the component or coupling agents are both present action of actinic light. in the light-sensitive layer, but they are prevent- One of the principal disadvantages of diazo ed from coupling to form an azo dye by one of type photographic papers has been the lack of several means; usually by the presence of acid stability in the white areas of the flnishedprint. in the light sensitive lay r, s nce up n s in- In one commonly used method for preparing o hibi d y aci uch Pap s a e p sed in he and using diazo-type papers, the paper (or other same manner as above described, and are then support as him, cloth, etc.) is coated with a layer d v p d y ali a one- This an e a plied comprising a light-sensitiv diazo compound, in the form of an aqueous solution, for example, which is capable, under proper conditions, or o ua solution of an alkaline salt of an alkali metal; pling with a azo-dyestufl-formlng component to 15 in which case the residue remaining after develform an azo dye. when such a paper is exposed opment is the same as in the previous case, and to light under a tracing or other-transparent discoloration proceeds in the same manner. positive to be duplicated the diazo compound in A third pe of diazo paper is sensitized with those areas which are transparent in the original diaZO p d and n y -w popositive is decomposed. In those areas which nent in acid medium, and after exposureisdevelare opaque in the ,original positive, the diazo p d y pa s ng t o h an a mosphere satucompoundisnot attested, rated with ammonia and water vapor. .Under Such an exposed paper i developed by applythese conditions, development occurs. However, ing to the exposed surface an azo-dyestuii-comdevelopment is gene l y slow by his m h d, ponent such as phioroglucinol o th phenolic and in additionthe fumes of ammonia are objeccompounds, in a solution made alkaline by the tionable. Speci ap r s must e P d o addition oi an alkaline salt of an alkali metal prevent pe of the a oma umes. and in or a mixture of such sa1ts,- I thi alkaline many cases the contrast between white and dark dium the azo-dyestufl component couples with areas is not as great as sirab e. the unaltered diazo compound in th ar a t According to this invention, by the use of aflected by light, iorming an azo dye. N couother alkaline substances in place of the alkali pling, of course-occurs in the areas which have metal Salts commonly s it is possible to rebeen exposed to light, I th o e commonly duce or eliminate this discoloration. We have referred to as the semi-dry process, the develfound that the use of volatile amines in the deoping solution is applied to th paper surface in veloping solution makes it possible to obtain sata thin film and the paper is dried without washisfactory developm nt f t exposed papers, and log or other means of removing unreaoted chemat the same time reduce the extent of the discolica'ls. oration of the white areas upon subsequent ex- Positive diazo prints prepared in this manner DOSlire Of the v p d p n s o li ht. While show desirable properties wh n fir t made, 40 the invention is not limited to the specific amines eluding satisfactory dark lines and satisfactory disclosed, but includes any volatile amine as dewhite areas, However, there r mai in th fined above, amines which can be used in this white areas aresidue which includes th d manner under this invention include diethylposition products of the diazo compounds, the amine, y m e, morpholine, nediazo-dyestuif-forming component oi. the developamine, monoamyl amine, and the various mether, and residual alkali from the developer. Unylamines. d o diti of exposure t light during use, The volatile amine can be applied in aqueous and particularly when the prints are exposed to solution, together with the azo-dyestufi-forming sunlight or other actinic light, these substances tomponent, to develop a a o P per which conreact to form yellow or brown colored products, lit-ins o y he i o mp d n th li ht sensiwhich discolor the white areas and reduce the V y r; or the volatile amine can be appli d contrast between the white and dark areas Varalone to a paper which contains the diazo comious means have been suggested and tried for pound and the azo-dyestufi-forming component overcoming this discoloration, including for ex- 1 e li h n i ive layer. 1

ample th use of reducing agents i the develop- A probable explanation for the reduction in er, but no method has been found which elimidiscoloration caused by the use of volatile amines nates the trouble, and diazo prints a made by as alkaline agents lies in the nature of the residues remaining on the whlteareas in the developed diazo print. The substances commonly,

line medium. It is believed that the discolora-. tion of the white areas is caused by oxidation of such' phenolic compounds, which is accelerated by any residual alkali remaining from the developer.

While our invention is not limited by this hypothesis,'this theory offers a possible explanation forthe beneficial eflect of the volatile amines used in developers according to this invention. A volatile-amine added to the developer renders it alkaline so that coupling between the diazo compound and the azo-dyestuif-forming component can take place. Upon subsequent drying of the moistened sheet, the amine being volatile evaporates, leaving no alkaline residue to accelerate discoloration. For this reason, discolora tion is reduced.

While it has been found that volatile amines in general produce a beneficial effect in stabilizing the white areas of the developed diazo paper, as described above, there are definite diiferences among the various volatile amines in the degree.

to which they prevent discoloration. We prefer the use of diethyl amine or morpholine, but the scope of this invention is not limited to these specific substances. 7 We have also found that it is advantageous to incorporate a non-volatile acid substance in the developer with the volatile amine, in a quantity less than an amount chemically equivalent to the quantity of amine used, so that the developer is alkaline in reaction (pH greater than '7) This has two eflects: Firstit reduces the alkalinity of the developing solution, thus aiding in preventin: deterioration of the developer before use, since oxidation and hence deterioration of the developer is greater in a moresalkaline solution. Second, it stabilizes the residue remaining on the paper after development, ensuring that it will remain slightly acidic after evaporation of the'ex cess amine. It is found that when a solution containing a non-volatile acid, and a volatile amine in excess, which has a pH greater than 7, is evaporated, and the residue dissolved in water, the pH of the resulting solution is less than '7. I Typical examples of such mixtures, with the pH of the original solution and the pH of the final solution, are given in the following Table I.

Team: I

Solution of residue Initial solution in water Solution Volume pH Volume pH Dlethyl mine (in excom) and oxalic acid.-- 25 ml. 10. 73 25 ml. 5. 90 Morgholine (in excess) an oxalic acid 25ml. 8.32 251111. 6.90

The data in Table I indicates that when a solution containing a non-volatile acid and a volatile amine'is evaporated, the residue remaining is invention, but are not intended to limit it there- Example I.0.6 g. of phloroglucinol and 10.0 g. of morpholine are dissolved in 100 ml. of water. Paper previously coated with a light sensitive diazo compound and exposed under a pattern or tracing is developed by lightly coating it with the above solution and allowing it to dry. The lines or dark areas are a deep red brown and the white ar eas are a clean white.

Other methods of applying the developer, such as by dipping or immersing the exposed print, or by spraying, can also be used, and are within the scope of this invention. Data on the pH of this solution, discoloration of paper developed as described above, and pH of a solution of residual material left on the paper after developing and drying are appended below in Table II.

Example II.-'-0.8 g. of phlor'oglucinol and 8.3 g.

of diethylamine are dissolved in 100 ml. of water.

A diazo paper made and exposed asdescribed amine 8.3 g., and oxalic acid, 6.8 g., are dissolved in 100, ml. of water. This solution is used as a developer in the manner described above orin any other manner.

Eazample IV.--Resorcinol, 0.5 g., diethylamine, 10.0 g. and oxalic acid, 6.8 g. are dissolved in 100 mlpof water.

E'axzmple V .Phloroglucinol, 0.3 g., diethylamine 9.2 g., oxalic acid 6.8 g., and resorcinol,

0.3 g., are dissolved in water, 100 ml.

Example VI.To the developer from Example III is added sodium thiosulphate, 10 g., and the solution is used as a developer as before. Improved stability of the white area results.

The following table gives data relative to the foregoing developers including pH as prepared,

relative whitenessofexposed areas on a commercial dia'zo-sensitized p per; immediately after development and drying, relativewhiteness' after exposure to sunlight, and'pH of washings from the paper afterdevelopmentand drying. Thesedataclearl'y show the increasedaeidity of the residue remaining on the paper'when'amines are used in the developer. For comparison, similar data with a commercial developer (designated as "Developer A), and ,with a developer prepared with a non-volatile alkaline salt and an amount of oxalic acid less than equivalent to the amount of alkali (designated as Developer B) are also given. The composition of Developer B is as follows:

Developer B 6.8 Water to make ml Developer A has the following composition Carbonate, as potassium carbonate -g Thiosulphate, as sodium thiosulphate-g Chloride, as sodium chloride g.. Phloroglucinol and resorcinol g 0.7 Water to make ml 100- TABLE II Characteristics of typical developers Relative pH of s whitewashe55 ness n ings alter Color of p devclan a exposure dark areas oped to sun- W I are:

Example I...- 9.34 5.75 7 6 Dark purp e. Example II. 11.15 5. 62 6 3 'Do. Example III. 8.13 5. 62 3 4 Do. Example IV.. 9.80 6. 91 1 l r a n g e brown Example V... 9.80 5. 70, 2 2 Brownlsh black Example VI. 8.18 5. 60 5 5 Daiik purp e. Developer A. 7. 97 6. 28 4 7 Bigliwnlsh 8 Developer B. $28 6.86 8 8 Dalik purl washings from an area 1" x 4 with ml. of distilled water. 1 l, whitest; 9, least white.

sulting from the use of volatile amines in the developer is clearly shown in the above table,

which shows that papers treated with Developers A and B after exposure to light had poorer whites than any of the other papers, even though Developer A showed quite good whites initially; while the darkening of papers developed in solutions containing amines was less serious.

We claim:

1. In a method of preparing diazo photo prints whereby discoloration of white areas" is inhibited, the step of developing such prints which comprises contacting the sensitized paper or similar supporting material with a developing liquid containing an azo-dyestufl-Iorming compound and a volatile amine, said developing liquid having a pH greater than 7.

.2. In a method or preparing diazo photo prints whereby discoloration of white areas" is inhibited, the step of developing such prints which comprises contacting the sensitized paper or similar supporting material with a developing liquid containing an azo-dyestufl-torming compound and diethylamine, the developing liquid having a pH greater than '7.

3. In a method 01 preparing diazo photo prints whereby discoloration of white areas is in-v hibited, the step of developing such prints which comprises contacting the sensitized paper or similar supporting material with a developing liquid containing an azo-dyestufl-forming compound, a volatile amine, and a non-volatile acid, the developing liquid having a pH greater than 7.

4. In a method of. preparing diazo photo prints whereby discoloration of white areas" is inhibited, the step of developing such prints which comprises contacting the sensitized paper or similar supporting material with a developing liquid containing an azo-dyestufi-forming compound, a volatile amine having a degree of volatility of the general order of that of diethylamine, and a non-volatile acid, the developing liquid having a pH greater than '1.

5. In a method of preparing diazo photo prints whereby discoloration of white areas is inhibited, the step of developing such prints which comprises contacting the sensitized paper or similar supporting material with a developing liquid containing an az'o-dyestuff-iorming compound in the form of a. phenolic substance and a volatile amine, said developing liquid having a pH greater than 7.

6. In a method of preparing diazo photo prints whereby discoloration of white areas is inhibited, the steps of efiecting development of said prints which include, contacting the sensitized paper or similar supporting material with a liquid volatile amine.

7. A developing liquid for diazo photo prints having the property of inhibiting discoloration of the white areas" of sensitized paper or similar supporting material after contact with said developing liquid, said developing liquid having a pH greater than 7 and containing an azo-dyestuff-forming compound and a volatile amine.

8. A developing liquid for diazo photo prints having the property of inhibiting discoloration of the "white areas of sensitized paper or similar supporting material after contact with said developing liquid, said developing liquid having a pH greater than 7 and containing an azo-dyestuff-forming compound and diethylamine,

9. A developing liquid for diazo photo prints having the property of inhibiting discoloration of the "white areas of sensitized paper or similar supporting material after contact with said developing liquid, said developing liquid having a pH greater than 7 and containing an azo-dyestufl-Iorming compound, a non-volatile acid, and I a volatile amine.

10. A developing liquid for diazo photo prints having the property of inhibiting discoloration of the white areas of sensitized paper or similar supporting material after contact with said developing liquid, said developing liquid having a pH greater than '7 and containing an azo-dyestuff-forming compound, a non-volatile acid, and diethylamine.

11. A developing liquid for diazo photo prints having the property or inhibiting discoloration of the "white areas" of sensitized paper or similar supporting material after contact with said developing liquid, said developing liquid having a pH greater than 7 and containing an azo-dyestuff-forming compound, a non-volatile acid, a volatile amine having a degree of volatility of the general order of that of diethylamine.

CLYDE A. CROWLEY. JOHN B MULLEN. 

